By 11 weeks both the blood and urine tests should be accurate. hCG levels rise rapidly, basically doubling every 3 days, and usually can be detected in about 2 weeks. They tend to peak at about 9-10 weeks or so.
It is unlikely you are pregnant.
Three "periods" also tend to indicate that you are not pregnant, even if light. Yes, you can have bleeding if you were pregnant however.
The only other thing you can do is an ultrasound at this point. A fetal heartbeat should be detected as well.